Conventionally, magneto-optical recording media using the magneto-optical effect have been known as an information recording medium with a large capacity capable of performing repetitive re-writing operations. And various studies and researches have been made in order to achieve high-density recording in the magneto-optical recording medium.
However, one of the disadvantages with this magneto-optical recording medium of this type is that when the diameter of a recording bit that forms a recording domain or when the interval of the recording bits is relatively small with respect to the diameter of a light beam spot focused on the recording medium, the reproducing characteristic deteriorates.
This is caused by the fact that in the case of the small diameter of a record bit or the small interval between record bits, since adjacent record bits are included within the spot of a light beam which has been converged on a target record bit to be reproduced, individual record bits can not be reproduced separately from other record bits.
Magneto-optical recording media, which are devised to overcome the above-mentioned disadvantage, have been proposed by reference (1) Japanese Laid-Open Patent Publication No. 150418/1994 (Tokukaihei 6-150418) and reference (2) "Ultra-high density magneto-optical disk using a magnetic-domain enlarging reproduction", 22pE-4 in papers of the 20th Symposium of Japan Applied Magnetics Society (1996).
In a construction described in reference (1) (hereinafter, referred to as the first prior art medium), a reproducing layer, which exhibits in-plane magnetization at room temperature and comes to exhibit perpendicular magnetization with temperature rises, is provided. Further, a non-magnetic intermediate layer is placed between the reproducing layer and the recording layer so that a magnetostatical coupling is realized between the reproducing layer and the recording layer.
Thus, the first prior art medium is designed so that the portion of the reproducing layer that is in the in-plane magnetization state is allowed to mask record bits (recording magnetic-domain information) of the recording layer corresponding to the above-mentioned portion. In other words, in the first prior art medium, this mask prevents record bits adjacent to the record bit to be reproduced from being included within the light beam spot, thereby making it possible to reproduce individual record bits separately.
In a construction as described in reference (2) (hereinafter, referred to the second prior art medium), a non-magnetic intermediate layer is interpolated between the recording layer and the reproducing layer in the same manner as the construction described in reference (1). Here, in this construction, a magnetic domain which is larger than the record bit on the recording layer is formed on the reproducing layer by a magnetic field generated from the recording layer. The reproducing system of this type, which carries out a reproducing operation by forming a magnetic domain larger than the record bit on the reproducing layer, is referred to as the magnetic-domain enlarging reproduction system.
However, it has been found that in the first prior art medium, when the diameter of a record bit is made extremely small, or when the interval between record bits is made extremely small, the intensity of the reproduced signal decreases, failing to provide sufficient reproduced signals.
Moreover, in the second prior art medium, a reproducing operation is not available unless the respective record bits are maintained in an isolated state. In other words, when the interval between the record bits in the recording layer is small (in the case of a high recording density), a plurality of record bits are located under the domain of the reproducing layer. In this case, the magnetic domain of the reproducing layer is subjected to magnetic fluxes (magnetic fields) from the plural record bits. That is, the problem with this construction is that it is not possible to apply only the magnetic flux from the record bit to be reproduced to the magnetic domain of the reproducing layer.